Motor fuel



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UNITED" STAT-ES PATENT orslca 1 Euphime V. York, N. Y.

No Drawing.

Application March 4, 1937,

Serial No. 128,929

This invention relates to motor fuels, and more particularly to motor fuels having a low temperature of ignition,' which are adapted for solid injection engines of theDiesel typ This application constitutes a continuation in part of my application Serial Number 49,027 filed 7 advantages of Diesel type or compression igni- -tion engines are greater fuel economy and smaller 15 fire risk. They also have a high thermal ef- 20 great favor and the high speed engine operates" 25 low octane number and it is desirable to change flciency, simplicity of operation and construction and the elimination of carbureters and magnetos. V

The high speed Diesel type engine is' finding more efficiently and effectively with a motor fuel .having' a high octane number. on the other hand most hydrocarbon products which aresuitable-for fuel with the-Diesel type engines have a the characteristics of the fuel in order to raise the octane number.- One of the important fuel characteristics attendant a high octane number is a prompt ignition accompanied by a high rate r so of flame propagation. Another characteristic is a low temperature-of ignition. The lower are the temperatures at; which compression-ignitionfuels 'ignite, the lower may be the compression ratio of the engine burning the fuel and the more 36 easily may the. engine .be started.

One important object of the present inventionis to provide an accelerator by which the buming characteristics of a compression-ignition fuel may be effectively changed to increase its cetane devalue.

an improvingagent or accelerator for'changing the iilll'nlng' characteristics of the" Diesel-type motor fuels by which the cetane value of the' sifuclmaybeincreasedinsubstantiallyadire'ct" proportion as .the amount of Some motor fuels; particularly cracked petw.

leTmdistil1ates,'and distillates Having a high compression ignition engines. v ,It is well known that the ignition quality of 15 V gine operation. Another object of the invention is to provlde.

- motor fuels to facilitate thelr'combustionin a a. slow rate of flame propagation and are quite difllcult to ignite. Accordingly suchfuels have not been satisfactory. for use in Diesel engines. Accordingly another object of the invention is to provide a chemical compo 1 treating 1117- drocarbon distillates, particularly petroleum dis tillates, which have a, slow rate of flame propagation and a comparatively, high temperature of ignition whereby the burning characteristics of such fuels may be changed to lowerthe ignition temperature and increase the rate of flame propagation and the cetane value of the fuel in order fuel in to improve combustion. characteristics of a motonfuel is dependent upon the chemical structure of the hydrocarbons in the fuel. Paraf:

- fln hydrocarbons are quite desirable as Diesel fuels while the oleflns and dioleflns, aromatics and fiaphthe'nes do not have as desirable burnso wing characteristics. Next to ignition qualities of a fuel may be considered in their'imp'ortance with reference to their burnlngcharacteristicsthe following properties: Viscosity, cleanliness,

boiling'range, carbon residue and sulfur. In

many types of Dieselengines, fuel is ignited by the heat of compression. In the engine design the maximum pressure is sought at which the fuel will ignite and it has been found that-with many fuels there is a period of delay after the maxi-' s0 mum pressure has been reached before the fuel ignites. The longer the delay period, the more rapid is the rise in pressure and the greater is the amount of the flnal pressure. It is desirable therefore to. minimize the duration of the de- 86- It is common toincrease the cetane value of Diesel'engine. Various ignition accelerators have been suggested. Among them are ethyl, propyl and butyl' nitrates, alkyl nitrites, organic mm 45:

compounds and nitro paraflins. :Some of these products have a distinct modifying value on the burning characteristics of fuel but none of them.

has proved tirely satisfactory. The nitrites cetanenumbcr ofa thermore these lower alkyl nitrates are explosive having low boiling point and flash point ranges and present a strong fire hazard. They also fail to improve startability sufiiciently. It has been found, furthermore, that the lower alkyl nitrates are not completely soluble in hydrocarbon motor fuels and therefore it is necessary to use a blending agent in order to get them into solution in the motor .fuels. Due to the low solubility of the compounds there is a tendency for the highly volatile low boiling alkyl nitrates to come out of solution and the presence of these vapors inthe fuel tanks is a dangerous fire hazard, as well as being very explosive.

One of the features of this invention is to provide an improved method of operating an internal combustion engine and particularly a compression ignition engine by burning the fuel therein in the presence 'of amyl nitrates-which act to herent in other accelerators and give a comparahaving a marked effect are the secondary butyl carbinitrate the primary iso-amyl nitrate and the tively large increase in the cetane value of hydrocarbon motor fuels. Amyl nitratesare more effeetive as ignition accelerators than lower alkyl nitrates. Of the eight isomers of amyl nitrates the normal primary amyl nitrate appears to have the most marked effect'on the cetane value of hydrocarbon motor fuels; Other amyl nitrates normal and the symmetric secondary amyl nitrates. These compounds are plentiful and comparatively cheap to manufacture. L The approximate ranges of boiling points of amyl nitrates are as follows: primary normal amyl nitrate boiling points 152-156 (2., secondary butyl carbinitrate 'boiling points 148-152 0., primary iso-amyl mtrate boiling points 146-l48 0., mixed primary amyl nitrates boiling points 146156 CQ, mixed secondary amyl nitrates boiling points 136-145 C., tertiary amyl nitrate boiling points 23- -27 C. at 4/5 mm.

These amyl nitrates which properly may be called pentyl nitrates are manufactured from corresponding alcohols derived from natural gas or petroleum products and have the followingmolecular formulae:

1. Normal primary amyl nitrate orpentyl ni trate-l, or normal butyl carbinitrate" CHaCHaCECHzCI-IzNOa 2. Primaryiso-amylnitrate, or iso-amyl nitrate,

'or 'iso-butyl carbinitrate..' a (CH3) =CH.CH:CH:NO:

3. Secondary butyl carbinitrate,-a primary amyl nitrate; CHJ.CH(C2H5) -CH2NO3 4, Methylpropyl carbinitrate or pentyl nitrate-2,

or a secondary normal amyl nitrate CHJ.CHI.CH2.CHNO3-CH3 5. Methyl-isopropylcarbinitrate, or a secondary iso-amyl nitrate (CHa)aCH.GHNOz.CHz

I posed largely of the secondary nitrates.

increase e. Diethyl carbinitrate or pentyl nitrate-.3, ora jsecondary amyl nitrate C2H5.CHNO3.C2H6

'I. Dimethyl ethyl carbinitrate or tertiary amyl nitrate (CHa) z.CNOa.C2Hs

The first three nitrates mentioned above are primary nitrates, the .next three are secondary and the seventh isomer is a tertiary nitrate. A1-

tion accelerating properties, the effectiveness of each isomer greatly differs from one another. They also lower the temperatures of the ignition of Diesel engine fuels. The most effective are the primary amyl nitrates. The secondary, such as the diethyl carbinitrate and methyl propylcarbinitrate are also quite effective as agents for im proving Diesel engine fuels, but are less effective than primary amyl nitrates. When the nitrates are made from mixed amylalcohols' derived from pentanes or from unsaturated petroleum hydrocarbons, such as for instance, amylenes or pentenes, we generally secure a mixture. In the first case such mixture is composed largely of primary nitrates and in the latter case a mixture is com- It has been found that these mixtures are very effective as agents for improving Diesel fuels and are technically and commercially practical for use in Diesel fuels.

It has been found that the increase in cetane value is substantially directly proportional to the percentage of amyl nitrates in the fuel. thermore the cetane value tends to increase along an almost straight line curve until more than percent by volume of the amyl nitrates has been used in modifying the fuel.

It has been found that the amyl nitrates are substantially completely directly soluble inmost hydrocarbon distiliates in all proportions, do not require the use of blending agents and are non-corrosive.

' The above isomeric compounds of the group of CsHnONOa were produced and tested individually, and in various mixtures with each other, in numerous Diesel fuels of various origins. The tests were made in standard Diesel testing englues using several known test methods and in Fur- ' though all sevenof these nitrates possess ignispeed service engines to determine their proper- I ties and effects and also the practicability for nition accelerator only when freshly made but i The tests have developed that the members of I after aging its effectiveness rapidly decreases it or partly destroying it and thus they impair their effectiveness asDiesel-fuel ignition accelerators in engines." I have found that, by removal of substantially all or of a larger part of sulfur and its compounds, 1. e. by d the sulfur content in a Diesel fuel the effectiveness of Diesel dopes" and especially of m nitrates if increased so greatly that the "cost of adding ignition accelerators to low-octane number comprcs sion ignition fuels is minimized.

The following examples may be cited withrcference to the properties of amyl nitrates:

Cetane Improve- Fuel med number ment Base fuel, a Mid-Continent gas oil.. 60 Base fuel plus 2% pentyl nitrates (mixed (70%) primary and (30%) secondary and tartiary amyl nitrates) 07 17 Base fuel plus 2% iso-amyl niirate. G 18 Base fuel plus 2% mixed primn'y amyl nitrates. 70 20 Base fuel plus 2% normal primuy amyl nitrate 72 j 2 The addition of 2% of various amyl nitrates to.

8: mary amyl nitrates. Pentyl nitrates comprised a mixture of about 10% primary (approximately 20% normal, 25% secondary butyl carbinitrate, 25% iso-am'yl): and of about 30% secondary amyl nitrates I (normal and diethyl carbinitrate) Mixed primary amyl nitrates comprised approximately 30% normal amyl nitrate, 55% secondary butyl carbinitrate and 15% iso-amyl nitrate. In tests with other fuels, where'the primary iso-amyl nitrate was added inlarger percentages it proved to be by almost 14% less efi'ective than the above described mixture of primary and secondary amyl nitrates. v

In order to establish the improvement of fuels in starting ability and in combustion the follow-' ing tests were made:

. O. 0.8. Cetane p v comm 0. QB. a

-- sioniatlo method mom Fae 1.55 ea 40' Faeto fuelplus2%miredprimary amy nitrates 7.02 '78 67- .Factoryiuelplus 4%mi xedprimary amyl nitrates 0.88 88 77 when larger of added the C. C. R;was reduced to as low as 5.03

and cetane value was increased to by both methods. It was evident from above that mixed. amylnitratesnotonlygreatly improve combustion characteristlcsofDieselfuelsincompres-. sion-ignition engines but also greatly facilitate the starting. The'ethyi nitrate and other lower alblnitrateshoweverarelackingthep operty ofsubstantially improving the starting.

The-following exampl ,show how sulfur and sulpho-compmmdscontentjin Diesel fuels affects or influences the effectiveness of amyl nitrates as ignition in ignition enh "if nitrate Total In vem tested sulfur :33; me m I percent numb cetaue High eetaue ("8hell) secondary refuence fuel (a strekht run I Bmail) a 0.84 74 cetene +1% mined nfimeryemyinlu-aiemn. 0.34 s4 10 eetane "8bell"+2% mined I llrluial'y i nithtel 0. M 02 1s oderatelmh octane fuel (a straight run gas oil)-. 0. M4 52. 5 +o 5% mired primary d so seeondary amyl nitrates 0.074 c6 12. 5 Moderaiel hill eetane fuel+ I 0.75% primary and secondary nitrates 0. 074 72. 4 l9. 0 Modanuly high octane fuel+l% mirednfirimnry and seeon amyl hates. 0.074 79. 5 27 Low cetaue pressure still recycle gasoiihu'ackedgesoil) 0.2! 37.5 Low ill recycl e gaso ,mixed (primsryan secondary) amyl nitrates 0. 26 48 10. 5 Low octane still rec cle gal oil+z7 amyl nitrates...-.-.. 0. Ii 59. 0 22.1

No sulfur or sulpho-compounds were added or 25 removed from the above Diesel fuels. The effectiveness of mixed amyl nitrates is decidedly greater with the diminishing of sulfur content in the above fuels. The ignition quality of natural Diesel fuels, that is a Diesel fuel distilled directly from a crude oil and which does not contain ignition accelerators, apparently does not change with either an increase or a decrease in the total sulfur content of the fuel. When, however, a given quantity of ignition accelerator is added to the fuel the ignition quality is appreciably better in the case of the fuel with the low sulfur content and the extent of the difference in' the ignition quality in favor of the low sulfur to 0.109% and the effect of various concentra- ,tions of the primary iso-amyl nitrate in the fuel was determined before and after desulfurizing of V the fuel toverify the improvement of its ignition quality in Diesel engine. vThe removal of this small quantity of 0.047% of sulfur content- (which acted as a catalytic poisoner") has rcsuited ina decided increase (by approximately 50%) in the effectiveness of ator in the fuels.

Ignition dela ceiane o.

' Total Improve- Fuel sulfur content 'Pmm one one awa 0.100 one area ciao aibmaackedgssoilu Qtinai fuel-P0596 iso-emyl ni- I isoamy on mi riliii'fi ho-em W m nfiitiuama "r nitrate. Desuifurlled -f uel+l% bo-emyi null Duuifuriled fuel+1.5% ice-amyl nimt that mm and mpho-eoiipounds which are present in Diesel fuels tend to the ignition acceleraccel- 7g" I been thus described what is claimed as new is:

1. A liquid fuel for compression ignition en- 4 erative property of amyl nitrates and therefore their removal is desirable, when amyl nitrates are used.

The above tests show that when the sulfur content of the hydrocarbon fuel is 0.05% by weight or less the effectiveness of the primary 1 amyl nitrates for ignition acceleration and increasing the cetane number is more than double its effectiveness when the sulfur content is above The preferred form of the invention having A liquid fuel qr the type defined m clam 1 bility of high sulfur Diesel oil comprising hydro- I wherein the pentyl nitrate may consist of a mixture of two or more nitrates of the defined group and wherein isobutyl 'carbinitrate may be mixed with one or more of the carbinitrates of the defined group. I

3.11 liquid fuel of the type defined in claim 1 wherein the petroleum distillate is a cracked petroleum distillate containing parafllnic, elefinic and other unsaturated hydrocarbons.

4. A liquid fuel of the type defined in claim 1 wherein the petroleum distillate is a cracked petroleum distillate containing paraflinia oleflnic and other unsaturated hydrocarbons.

5. A liquid fuel of the type defined in claim 1 in which the petroleum distillate is a mixture of straight-run and" cracked petroleum distillates containing oletinic, paraflinic and other unsaturated hydrocarbons.

6. A liquid fuel of the type defined in claim 1 whereinthe hydrocarbon distillate is refined to reduce the sulfur content to less than .25 per-g cent by weight of the distillate prior to addition of the nitrate to, the distillate.

'7. A process of enhancing the cetane susceptibility of high sulfur Diesel oils comprising hydrocarbon distillates of the gas 011 type comprising refining the distillate to reduce the sulfur content to less than .25 percent by weight of .the distillate and dissolving in the distillate a-pentyl nitrate selected from the group consisting of normal butyl carbinitrate, secondary butyl carbinitrate, methylpropyl carbinitrate anddiethyl carbinitrate. I

8. A process of enhancing the cetane suscepticarbon distillates of the gas oil type comprising refining the distillate to reduce the sulfur content to' less. than .25- percent by weight of the distillate and dissolving a mixture of two or more pentyl mtrates in the distillate selected from the group consisting of normal butyl carbinitrate, secondary butyl carbinitrate, methylpropyl carbinitrate and diethyl carbinitrate'and wherein isobutyl carbinitrate may be mixed with one or more of the nitrates of .said group.

' EUPHIME V. BERESLAVSKY. 

